Prospect of developing Nd–Fe–B-type magnet with high electrical resistivity
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Nd–Fe–B-type magnet is exclusively used as a rotor magnet in the traction motor of hybrid electric vehicle (HEV) and electric vehicle (EV), but its overly high operating temperature is a lingering problem attached to the magnet. The major cause of the high operating temperature is eddy current, which is readily generated in the highly conductive metallic magnet under alternating magnetic field from stator ripple. In this article, temperature rise in the Nd–Fe–B-type magnet with varying electrical resistivity under alternating magnetic field is discussed with the intention of highlighting the importance of enhancing the electrical resistivity for reducing the operating temperature of the Nd–Fe–B-type rotor magnet. Temperature rise in the Nd–Fe–B-type magnet (dielectric salt-added die-upset magnet) with high electrical resistivity is noticeably lower compared to the magnet (commercial sintered rotor magnet) with lower electrical resistivity, substantiating the theory that enhancing the electrical resistivity in the rotor magnet is fairly effective for suppressing the over-rise of its operating temperature during operation. Die-upset process is revealed to be particularly pertinent for the fabrication of highly dense salt-added magnet with high electrical resistivity.
KeywordsRare-earth magnet Nd–Fe–B-type magnet Rotor magnet Operating temperature Eddy current Electrical resistivity
This work was financially supported by the Technology Innovation Program from the Ministry of Trade, Industry and Energy (MOTIE, Korea) (No. 10080382). The authors would also like to extend thanks to Professor K. H. Shin in Kyungsung University for invaluable assistance for evaluating the temperature rise in a magnet.
- Dajaku G, Gerling D. An accurate electromagnetic and thermal analysis of electric machines for hybrid electric vehicle application. In: The 22nd International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium and Exposition, Yokohama, Japan. 2006, 1.Google Scholar
- Nollau A, Gerling D. A new cooling approach for traction motors in hybrid drives. In: International Electric Machines and Drives Conference, Chicago, USA; 2013, 456.Google Scholar
- Itoh K, Hashiba Y, Sakai K, Yagisawa T. The A.C. losses of the rare-earth permanent magnets. Trans Inst Electr Eng Jpn. 1998;118(2):182.Google Scholar
- Polinder H, Hoeijmakers MJ, Scuotto M. Eddy-current losses in the solid back-iron of PM machines for different concentrated fractional pitch winding. In: IEEE International Electric Machines and Drives Conference. Antalya, Turkey. 2007:652.Google Scholar
- Nuscheler R. Two-dimensional analytical model for eddy current loss calculation in the magnets and solid rotor yokes of permanent magnet synchronous machines. In: 18th International Conference on Electric Machines. Vilamoura, Portugal. 2008: 1095.Google Scholar
- Wills DA, Kamper MJ. Reducing PM eddy current rotor losses by partial magnet and rotor yoke segmentation. In: The International Conference on Electrical Machines, Rome, Italy. 2010.Google Scholar
- Yokoyama Y, Iwata K, Fujiwara K, Takahashi N, Kubo T. Basic study on loss of permanent magnet due to AC field. National Convention Record IEE Japan. 2001: 2.Google Scholar
- Aoyama Y, Ohashi K, Miyata K. Experiment and analysis of eddy current loss in permanent magnet under alternating magnetic field. Papers of technical meeting on rotating machinery, IEE Japan, 2002;135: 13.Google Scholar
- Kanazawa S, Takahashi N, Kubo T. Measurement and analysis of AC loss of NdFeB sintered magnet. IEE J Trans Fund Mater. 2006;154(4):869.Google Scholar
- Fedorov P. Systems of Alkali and rare-earth metal fluorides. Russ J Inorg Chem. 1999;44(11):1703.Google Scholar